4 Wheel Drive/SUVs: clunk is coming from transfer case, haynes manual, axle shaft

Question
Carl,
Thank you for your quick response.  I removed the Driveshaft last night and started it up and let out the clutch.  It is definately coming from transfer case.  Checked the fluid level and was almost dry.  Filled it up and clunking is still there.  I beleive it got too dry and broke a couple of teeth off the gear that is driven by the chain.  The splines on transfer case and driveshaft were fine.  The binding and noise always happen at the same location when the driveshaft is turning.  It is not sporadic.  Checked all the caps and u-joints when I had the driveshaft out and although they are old, still in working condition.  I have a local mechanic who is willing to diagnose and replace the transfer case.  My follow up question is this....is it possible to remove and replace the transfer case without having to remove whole transmission?  My Haynes manual says the two should be removed and reinstalled as one piece but doesn't say why, and I can't figure out what linkage relationship they have.  Once the transmission is out, you unbolt the old transfer case and bolt on the new one and re-install the whole thing.  Doesn't make sense to me why you need to remove transmission.  What are your thoughts?  Thanks again for your time.  Travis
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Followup To
Question -
Hello,
I have a 94 Wrangler I6, 4.0, 5spd stick. While parking the boat in the back yard, my jeep started making a "clunking" whenever I let the clutch out. (As if the driveshaft were hitting something every time it made a rotation) I put it up on 4 jack stands and checked Front axle shaft u-joints...all good. Looked at Front and Rear driveshaft u-joints, nothing obviously wrong, no wiggle. Started it up and let out clutch, "clunking" sounds like it is coming from transfer case. Rear driveshaft doesn't seem to wobble. Can turn the rear driveshaft by hand 3/4 of way and then it becomes harder to turn (binds) and then it eases up for another 3/4 of turn. Can't tell if problem is u-joints, driveshaft, differential or transfer case. Is there a way for me to narrow down possible problem? Am thinking about removing rear drive shaft to take closer look at u-joints and see if "clunk" still occurs without driveshaft connected. What are your thoughts? Thanks for your time. Travis
Answer -
Travis,

Normally, I would suspect a u-joint, or drive line problem.  In your case, since you checked these out, the first thing I would do, would be to pull the cover off of the rear differential, and check the gears.  It's possible that you have a bad spider gear, or a tooth missing on the ring gear.  The next thing to check would be the transfer case.  You should have a NP231 transfer case, which is chain driven.  There is a chance that the chain is stretched to a point where it is banging from taking up slack.  These transfer cases are, fairly easy to work on if you are so inclined.

You can purchase a manufacturer's shop manual for the Jeep, but they are quite expensive, normally costing, around $100.  A Chilton's or a Hayne's manual can be purchased at most auto parts stores for $20, and they have a lot of information on basic trouble shooting, and repairs.  These manuals are designed for a year or range of years for specific vehicles, and are invaluable if you are planning on doing any repairs yourself.

Carl  

Answer
Travis,

I'm not sure why they say that you need to remove the transmission.  I have removed my transfer case a couple of times to do upgrades, and had no problem removing just the transfer case.  The transfer case, has it's own linkage, separate from the transmission.  When you rebuild the case, make sure that you replace all the seals, and bearings.  It might be a good idea to replace the pump also.

Carl